Sewage treatment apparatus



' Jan. 17, 1939.

C. -H. NORDELL S EWAGE TREATMENT APPARATUS Filed March 18, 1935 3 Sheets-Sheet l g o o a o I e e e a (mi W/EQQQZM u a u a o o g a v a .jV/Vo'rael/ v Jan. 17, 1939. c. H. NORDELL SEWAGE TREATMENT APPARATUS Filed March 18, 1935 s Sheets-Sheet 2 I Jya/egmzzr,

I CkrZfl/Vaza/all ject sewage and activated sludge to aeration in Patented Jan. 17, 1939 SEWAGE TREATMENT APPARATUS Carl H. Nordell, Chicago, 111., assignor to Advance Engineering Company, Chicago, lit, a corporation of Illinois Application March 18, 1935;, Serial No. 11,554

.15 Claims. cl. 210-8) This invention relates to sewage treatment apparatus and particularly to difiusers for supplyingair in sewage treatment processes.

In sewage treatment, it is well known to subaeration tanks and for this purpose it is well known to employ long tanks or a series of tanks through which the mixed liquid flows. Such tanks are provided with diffusers for the purpose of supplying large quantities of air thereto in finely. divided condition. The purification operation is accompanied by the consumption of oxygen and one of the main effects of the introduction of air is to supply and replenish this oxygen. Another effect of the introduction of the air is to cause a rotation of the mixed liquids in the tank, which rotation efl'ectively prevents settling out of solid-and heavy materials.

Heretofore it has been usual to provide such tanks at or near the bottom with plates of porous or foraminous'material through which the necessary air is supplied. A diffuser system possesses many serious objections. In the first place, to

replace a diffuser plate it is,necessary to stop the process and empty the tank, and it must be borne in mind that these tanks may be very,

very large. ,A further objection is that the liquid in the tanks goes into awhirling or rotating motion which passes near the edges of the difiusers'.

The tendency is for the whirling mass to localize the path of the air delivered by the diffuser plates into a relatively narrow band of the liquid. This localization is very objectionable from the point of view of efiicient dissolution of oxygen in the liquid. Another serious objection of the diffuser systems heretofore known is that there is a substantial tendency for solid materials to deposit.

upon them, thus reducing their air passing emciency. This .occurrenceds believed to be due to the reduced specific gravity of the liquid above the diffuser plates, owing to the presence of a very large amount of air therein. It is believed that solid or nearly solid materials which are just able to remain suspended in flowing water or sewage, drop out of the lighter column of air and liquid which exists above the difiuser plates.

The'principal objects of the present invention 'are to provide an improved difiuser system which will be free from these advantages, which will be economical and simple to construct, and which can readily be serviced without emptying the taken on the line 9-9 of Fig. 2, and

the invention. will appear from the following (I scription of preferred embodiments thereof,taken in conjunction with the accompanying drawings, in which a Figure 1 is .a cross section of an aeration tank equipped with aerators embodying my invention;

Fig. 2 is a fragmentary plan view, taken on the line 2 -2 of Fig. 1;

Fig. 3 is a iragmentary'sectional elevational view, taken on the line 3-,3 of Fig. 1;

Fig. 415a sectional view through a difiuserelement, taken on the line H'of Fig. 3, and on a somewhat larger scale; s

Fig. 5 is a fragmentary sectional view on a still larger scale, taken on the line 55 of Fig. 4;

Fig. 6 is a perspective view of a difiuser plate included in the embodiment of the invention illustrated in Figs. 4 and 5; I

Fig. 7 is a sectional view similar to Fig. 5, showing a modified form of diffusing element:

' i Fig. 8 is a perspective view of such a diffuser.

element;

Fig.. 9 is a fragmentary sectional detail view,

Figs. 10 and 11 are sectional views similar to Figs. 5 and 7, showing rurther modifledformsof diffusing element.

Referring to thedrawin'gs, and particularly to Fig. 1, which shows an aeration tank I, it is pointed out that'this aeration tank may have a cross section as shown in Fig. 1 and be of indeter minate lengths Incoming sewage, together with activated sludge, moves progressively and relatively slowly through the aerating tank I, during which time it is subjected to aeration introduced by a diffuser system. Diffuser systems as heretofore used have been subject to a great many disadvantages. The successful treatment of sewage depends to a considerable extent upon the eflicient dissolution of atmospheric oxygen in the mixed liquid in the aerating tank. It is, therefore, very advisable to endeavor to introduce the air in a very finely divided condition, th t is. in the form of fine bubblesin order that a get amount ofoxygen may come into contact with the liquid and may dissolve therein. This calls for difiuser plates having relatively flne openings. The bubbles of air introduced into the mixed liquid ascend therein and pass upwardly to the surface. The air is normally supplied at one side and the result of the upward movement of the bubbles is to cause a rotary movement of the mixedliquid to take place. The rotation of; the mixed liquid has the eflect of keeping solid material in suspension so that it may pass along out- - to the presence in it of a large volume of air bubbles. As a result, a certain amount of solid matter which would normally remain suspended in water, becomesdeposited on the diffuser plates, reducing their efliciency.

In, the preferred embodiment of the invention illustrated, I mount an air main l I on one of the side walls of the aeration tank It]. The air main ll may extend the whole way along this tank or several lengths of such air main may be employed. As best seen in Fig. 1, the air main H- is preferably located belowthe normal level of liquid in the tank III. on the air main II I mount a series of Ts [2, each provided with a valve 13 controlling admission of air thereinto. The Ts l2 are provided at each end with stufling boxes l4 whereby pipes [5 may be rotatably mounted ther ein while preserving an air-tight condition. It may be noted that slight leaks of air do not mattersince the pipes l5 so that the supply of air can be regulated along the length of the tank or'may be-cut off from any individual aeration .unit depending from one of the pipes l5.

The pipe I5 is providednear. its ends with two Ts Hi from which depend two pipes l9. The pipes 19 communicate freely with a long chamber 23 of box-like form which is approximately as long as the pipe I5 from which it depends. The

- chamber 20 is provided with a series of openin 2| along its length, which openings communicate into the interior of a series of difl'user elements 22. As best seen in Fig. 1, the diffuser elements 22 are horizontal and extend outwardly from the chamber 20 in the transverse direction of the aeration tank In. E

On each of the pipes I5 I mount a sprocket wheel 23 over which I pass a chain 24. The chain also passes over a small sprocket, wheel 25 rotatably mounted in a bracket-26 at the top of the tank It. The sprocket 25 may be actuated by a crank handle 21 so as to rotate the pipe l5. When this is done the container 20, together with the diffuser elements 22," are elevated up into the position shown in dotted lines in Fig. 1. It will readily be seen that the air may be shut ofl by the appropriate valve l3 and any of the aeration elements adjusted, repaired or cleaned. Any suitable means,,such as a hook 28,, may be provided for holding the elements referred to in their upper position'while the work is being done. The return of the aeration elements to their operating position can rea y be accomplished, due precaution being taken to prevent violent impact with .the wall of the aeration tank.

(a trated by arrows in Fig. 1. This rotation is in the same direction as the uprising air and thus, to some extent, the period of contact between the air bubbles and the liquid is shortened. I prefer to provide on the opposite wall of the tank It] similar ancillary aerating equipment as shown in Fig. 1. This, ancillary equipment is mainly similar to that previously described and corresponding parts 4 liquid flows upwardly between the units 22. 'The' units 22 and 22' are stream-lined for these directions of flow since it is desired that the rotating liquid should pass to the fullest extent'through the aerating systems. The air admitted by the aerating units 22' is carried downwardly and across the tank by the rotating liquid and consequently executes a long circuitous path therein, which is conducive to a very eflicient dissolution of its oxygen in the liquid. The features of the aerating element 22 constitute an important part of my invention and they will now be described in detail.

Referring particularly to Figs. 4, 5 and -6, the embodiment of diffuser eleme t shown therein comprlses a lower support arm which is suitably a hollow casting provided at its inner end with a flange 30 whereby it may be secured to the housing 20-by means of bolts 3|; Along opposite edges the arm 23 is provided with inclined seats 32/ which serve as abutments for diffuser plates 33. .The upper edges of the diffuser plates 33 are chamfered as shown at 34 and these edges abut against the underside of an upper hollow arm 35 which is provided with a flange 36 where by it'is bolted tothe housing 20 by bolts 31.

' Suitable gaskets 38 and 39 are located between the diffuser plates 33 and the portions of the arms 23 and 35 against which they abut. Any suitable number of plates 33 may be provided along the diffuser element .22. These plates. are held in position by an end cap 40 which is bolted to the outer ends of the arms '23 and 35. Suitable gaskets 4| are provided between adjacent difiuser plates and between the cap 40 and the last diffuser plate. A gasket 42 on the face of the chamber 20 serves to prevent entrance of fluid into the interior of the arms 29 and 35. It will be understood thatthe lengths of the diffuser plates. 33 and the thickness of the gaskets 4| enable the cap 40 to apply an effective pressure upon the gaskets. If necessary, additional gasketmate-- rial may be applied in order to attain this pressure, which should be sufflcient to prevent any substantial leakage except through the pores of the diffuser plates.

v I prefer to provide means at points interfiiediate with the length of the diffuser element 22 in order to maintain air-tight relationship between the diffuser plates 33 and the arms 29 and 35. Such means may suitably comprise loops of wire 43, the ends of which are secured in openings 44 of jabar ,45. -.The bar 45 may suitably be located below, the arm 29. The bar 45 has threaded openings which receive bolts 46. These bolts 46 are upwardly directed and abut against the underside of the arm 28. It will readily be understood by reference to Fig. that by tightening the bolts 46 a very substantial force may be applied upon the arms 29 and 35, holding them firmly against the plates 33 and compressing the gaskets 38 and 39 into air-tight pondition. It will thus be understood that the plates 33, the arms 29 and 35 and the cap to constitute, in each diffuser element, an air chamber which receives air from the chamber 20 through the opening 2|. The opening 2| is preferably triangular in shape and substantially conforms to the shape of the air chamber within the diffuser element.

The embodiment of difiuser element illustrated in Figs. 7- and 8 differs from the embodiment just described principally in the fact that the difiuser material is. made in the form of a duct or pipe 41. The underside of the duct or pipe 41 bows downwardly so as to fit the upper face of the lower arm 29. The upper face of the conduit. member 41 is' bowed upwardly so as to cooperate with the' seat provided by the upper arm 35. Suitable gaskets 48 and 49 are provided between the duct member M and the arms 29 and 35. The pipe sections l'l may be mounted and held in leak-tight relation in the same manner as the embodiment first described. In Fig. 7 I show the arms 29 and 35 braced together by a wire loop 50. This loop passes under a longitudinal bar 5| which carries bolts 52. By tightening these bolts force is applied, tending to draw the arms .29 and 35 together in a manner very similar to the wire 43 in the embodiment first described.- i g i The embodiment of difiuser element illustrated in Fig. includes provision for compensating for the difference of head between the higher and lower portions of the diffuser plates 33.; -0wing to the lower hydrostatic pressure there is a tendency for the'higher portions of the plates to .transmit more air. Tosome extent this air is delivered in the form oflarger bubbles which are inefiicient for the dissolution of oxygen in the liquid. In this embodiment I chamfer off the upper ends of the diffuser plates 33 and place the chamfer faces together in air-tight relation. This relation may be attained by a gasket or cement 53 interposed between these chamfer faces.

In this embodiment straps 54 are provided, the ends of which are welded at 55 to form loops. A

not '56 is welded to the strap in alignment with an opening therein. The strap may be tightened by a bolt 51 threaded into said nut and abutting against an abutment 58 mounted on'the arm 35. In the embodiment of the invention shown in Fig. 11, I correct the tendency of the air to pass more freely through the higher parts of the diffuser plates 33 by tapering these plates downwardly to a slight extent. The greater resistance of the upper part of the plate substantially prevents a larger amount of air passing therethrough owing to the lower hydrostatic pressure than prevails at the lower part of the plate. One advantage of uniform air passage through all parts of the-plate is that the bubbles are ,moreuniform in size and on the whole are smaller. The smalle er the bubbles are, the more effeotively does the liquid dissolve oxygen therefrom.

It will be readily understood that any suitable number of diffuser elements 22 may be mounted on any individual chamber 20. Thus, with reference to Figs. 2 and 3, it is to be noted that I provide seventeen such elements on one chamber 20'. ,These elements are located in parallel relation and are substantially spaced so that liquid may ascend may between them. It will be noted that these elements are streamlined for liquid flowing in the upward direction. In other words, the exposed diffuser plates and the upper arm 35 are formed to establish an upwardly directed apex. As previously mentioned, the diffuser elements 22' are inverted and are stream- I lined to present the least resistance to the downward flow of liquid between them.

Referring more particularly to Fig. 1, it will be noted that when the valves l3 are opened air is supplied from the main ll into the numerous diifuser elements 22. The diffusing material of which the plates 33 or the ducts 41 are made, enables the air to pass into the liquid in the tank ID in the form of small bubbles, which rise to the surface. In so rising a'considerable amount of their oxygen is dissolved in the (liquid, the amount depending upon the smallness of the bubbles and the amount of oxygen already held in solution in the liquid. The upward passage of these bubbles causes the liquid to move upwardly and the result is that the fluid rotates in the manner indicated by arrows in Fig. 1. It will be noted that the liquid moves upwardly between the diffuser elements 22 so that the air delivered therefrom becomes intimately mixed with the main body of liquid. In diffusers heretofore employed, the rotating liquid has to move obliquely pastthe diffuser system, with the result that there was a considerable tendency for the delivered air to be vconfined into a layer immediately outside of the main rotating mass, leading to low efficienpy of oxygen dissolution. 'Bythe present invention this objectionable feature is completely overcome.

One of the dimculties experienced with diffusers heretofore known has been the tendency for solid material to deposit upon the diffusing plates. This phenomenon is believed to be due to the fact that the specific gravity of the column above the diffuser is substantially lowered by the presence of a large amount of air. Consequently, certain solid materials which are sufficiently heavy so that they will just remain S115.- pended in moving water or sewage, willsink in the column of air and water. In the present construction such heavy materials merely fall between the adjacent diffuser elements 22 and no trouble is caused thereby.

After the valves l3 are opened and the liquid in-the tank It is put into rotation, the valves l3 are opened to admit a lesser amount of air. The air thus admitted is carried down and around by the rotating liquid and thus executes a long circuitous'path before it escapes to the surface. This prolonged contact with the liquid is highly favorable for the eflicient dissolution of the oxygen from the fine bubbles into the liquid.

Although the-invention has been described in embodimentsthereof, it must be understood that such details are not intended to be limitative of the invention except in so far as set forth in the accompanying claims.

Having'thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

connection with the specific details of preferred 1. In sewage treatment apparatus, in combination, an aeration tank, and an aerating system comprising a multiplicity ofaerating conduits adapted to transmit air located in spaced relation in said'tank at a substantial height therein, each of said conduits being of streamlined cross-section and having upwardly sloping diffusing walls to permit,.circulating liquid to-pass between them with slight resistance.

2. In sewage treatment apparatus, in combination, an aeration tank, and an aerating system comprising a multiplicity of parallel spaced aerating conduits spaced from the walls adapted to transmit air, said conduits being 'of streamlined cross-section to permit the liquid to pass there between with slight resistance.

3. In a sewage treatment apparatus, in combination, an aeration tank, and means therein imparting a rotary movement to liquid therein including a'conduit having a normally stationary position at a substantial height in said tank having upwardly sloping air transmitting walls, said conduit being of streamlined cross-section in the direction of said movement.

4. In a sewage treatment apparatus, an aeration tank, an aerating system comprising air discharging elements having a normally stationary position at an intermediate height in said tank, and means pivotally supporting said elements above said intermediate heights and sufliciently remote from a wall of the tank to enable the elements to be swung out of the tank.

5. In a sewage treatment apparatus, an aeration tank, an air supply pipe extending longitudinally thereof, and an aerating system pivotally mounted 9n, and in communication with said pipe, said system comprising a multiplicity of air discharging conduitsin spaced relation hav ing a normally stationary position at an inter- I mediate height in said tank, between which the liquid'in said tank is adapted to pass freely, said air supply pipe being located above the conduits and sufiiciently remote from a wall of the tank to enable said conduits to be swung out of the tank. V

.6. In a sewage treatment apparatus, an aeration tank, means having a normally stationary position adjacent the bOttOM the tank and near one side thereof for injecting air into liquid in the tank, and means having a normally stationary position adjacent the other side and at a substantially higher location for injecting a lesser supply of air into said liquid.

'7. In a sewage treatment apparatus, an aeration tank, means having a normally stationary position adjacent one side of the tank for injecting air into liquid in the tank, and means having a normally stationary position adjacent the other side for injecting a lesser supply of air 'into said liquid, each-said air injecting means comprising a multiplicity of horizontal units in spaced relation located sumciently high to permit said liquid to pass freely therethrough.

8. In a sewage treatment apparatus, an aeration tank, means having a normally stationary.

. position adjacent the bottom of the tank and near one side thereof for injecting air intoliquid arnet in the tank, and means having a normally stationary position near the dther side and at a substantially higher location for injecting a lesser supply of air into said liquid, each of said air injecting means comprising a multiplicity of horizontal units in spaced relation located sufilciently high to permit said liquid to pass freely there-,

through. I

9. In a sewage treatment apparatus, an aeration tank, an air iniecting device therein having a normally stationary position, means substan-- tially above said air injecting device pivotally supporting said device and mechanical means for swinging said device upwardly about its pivotal support out of the tank, said support being sufiiciently remote from a wall of the tank to permit 1 such swinging.

} prising top andbottom bars mounted on saidheader and extending therefrom, and convergent sides of diflusing material therebetween.

12 A hollow diffuser element comprising a top bar, a bottom bar,'convergent side plates of diffusing material therebetween and encircling tension means rigidly securing said top and bottom bars together, said bars including mounting means whereby the elements may be mounted in operating relation.

13. A hollow diffuser element comprising a top bar, a bottom bar, and an integral conduit of diffusing material secured therebetween.

14. A hollow diffuser element comprising, two

upwardly sloping diffusing plates on opposite sides, a bar' extending along the upper edges of the plates establishing an air tight relation between the upper portions of the diffusing plates, and means at the lower ends of the plates forming therewith an air chamber, said bar anddower means cooperating with the angularly related e'dgeseto prevent removal of the diffusing plates.

15. The method of treating sewage which consists in passing it through an aeration tank, in-

troducing air at one stationary position therein thereby inducing a rotary movement of the sewage in vertical planes, and supplying additional air to the sewage at astationary position where it is moving downwardly.

- CARL H. NGRDELL. 

